Hard-coated film, method for production thereof and antireflection film

ABSTRACT

There is provided a hard-coated film that includes a thermoplastic film and a hard coat layer placed thereon, has high surface hardness, is prevented from forming interference iris patterns, does not reduce image sharpness when used for antireflection films, and is prevented from causing screen glittering, external light reflection, or coloration irregularity of reflected light. The hard-coated film includes a polyester film and a hard coat layer placed on at least one side of the polyester film, wherein the hard coat layer has a surface with irregularities, an interface between the polyester film and the hard coat layer has irregularities, and the surface of the hard coat layer has 3D surface roughness parameters including an arithmetical mean deviation of surface Sa of from 15 nm to less than 150 nm and a kurtosis of surface height distribution Sku of from 1.5 to 5.

TECHNICAL FIELD

The invention relates to a hard-coated film and a method for productionthereof and also to an antireflection film therewith. More specifically,the invention relates to a hard-coated film suitable for use in displayantireflection film or touch panel film, characterized in that it hasexcellent scratch resistance and less interference iris patterns andproduces very little coloration irregularity of reflected light afterthe surface layer is subjected to antireflection treatment, andparticularly characterized in that it is effective in preventingreflection, providing transmission image purity, and reducing screenglittering when used as an antireflection film for a plasma displaytelevision filter.

BACKGROUND ART

Biaxially-oriented polyester films have advantageous characteristicssuch as mechanical characteristics, dimensional stability, heatresistance, transparency, and electrical insulating properties andtherefore are used for various applications such as magnetic recordingmaterials, packaging materials, electrical insulating materials, avariety of photographic applications, graphic arts, and optical displaymaterials. However, they do not have sufficient surface hardness andtherefore have the disadvantage that their surface can be easily damagedby contact, friction, or scratching with other hard materials. In orderto solve this problem, conventional techniques use methods of placingvarious hard coat layers.

Since biaxially-oriented polyester films are highly crystal-oriented,hard coat layers directly provided thereon may have insufficientadhesion. Therefore, methods of providing a hard coat layer on apolyester film through an adhesive layer are generally conducted.

When such methods are used or when a hard coat layer is provideddirectly on a biaxially-oriented polyester film, a refractive indexdifference in-plane can be generated between the hard coat layer and theadhesive layer or biaxially-oriented polyester film in contacttherewith. Therefore, when such a structure is used as a substrate foroptical applications such as antireflection films or touch panel films,interference iris patterns can be generated depending on unevenness inthe thickness of the hard coat layer.

In the applications described above, the formation of interference irispatterns significantly inhibits the clear view properties of displays.In order to reduce this phenomenon, the coating thickness accuracy isimproved, or the refractive index of the hard coat layer is increased sothat the difference between the refractive indices of the hard coatlayer and the base film can be reduced (Patent Document 1). Alsoproposed are a method including the steps of embossing the surface of abase film by hot pressing to form irregularities on the surface andproviding a hard coat layer on the embossed surface (Patent Document 2),a method including the steps of using a solvent capable of dissolving abase film to form a hard coat layer-forming coating composition andapplying the coating composition to the base film so that the basematerial can be dissolved or allowed to swell (Patent Document 3), amethod of transferring a molding film (Patent Document 4), and a methodincluding the step of adding particles to a hard coat layer to formirregularities for scattering light (Patent Document 5). However, therefractive index of the hard coat layer or the adhesive layer cannot becompletely adjusted to about 1.60-1.65, the typical refractive index ofbiaxially-oriented polyester films, and existing techniques are notsatisfactory and cannot completely eliminate interference iris patterns.It is also very difficult to provide a hard coat layer with a uniformthickness such that interference iris patterns can be prevented.

When the method including the steps of forming irregularities on thesurface of a base film by hot pressing or the like and providing a hardcoat layer thereon is only used, the reflection-suppressing effectcannot be sufficiently achieved, although interference iris patterns canbe made slightly less visible. Since biaxially-oriented polyester filmshave high solvent resistance, few solvents are suitable for the methodof dissolving a base film or allowing a base film to swell, andortho-chlorophenol, the only available solvent, has a problem in whichit can pollute the working environment or is not easy to remove. When amixture layer is formed in the interface between the base film and thehard coat layer, the haze can increase, and the sharpness of thetransmitted image from a display using such a technique can be reduced.In this case, since the hard coat layer is made relatively smooth, theexternal light reflection-reducing effect cannot be expected.

Typical hard coat layers are very smooth. Therefore, when such hard coatlayers are subjected to antireflection treatment, the intensity ofreflected light from the resulting antireflection layer surface can havea significant wavelength dependency so that a certain color can bestrongly visible or color heterogeneity can be caused by unevenness ofthe antireflection layer coating.

The method of transferring the irregularities of the mold film to thehard coat layer can cause contamination with foreign matter from themold film and can form irregularities with relatively large slopeangles, which can easily cause screen glittering. The method of addingparticles to the hard coat layer to form irregularities on the hard coatlayer surface can produce the effect of preventing interference irispatterns or reflection but still has a problem in which it can increasescreen glittering and therefore reduce clear view properties.

-   Patent Document 1: Japanese Patent Application Laid-Open (JP-A) No.    2002-241527-   Patent Literature 2: JP-A No. 08-197670-   Patent Literature 3: JP-A No. 2003-205563-   Patent Literature 4: JP-A No. 2004-341553-   Patent Literature 5: JP-A No. 2003-75604

DISCLOSURE OF INVENTION Problem to be Solved by the Invention

An object of the invention is to provide a hard-coated film and anantireflection film therewith that can solve the problems describedabove, exhibit reduced interference iris patterns or reduced colorationirregularity of surface reflected light, and be effective in producingsharp images, reducing screen glittering, and preventing reflection whenused for a front face filter of a plasma display television.

Means for Solving the Problems

Investigations have been made to achieve the object, and as a result,the invention provides the following features:

(1) A hard-coated film, including: a polyester film; and a hard coatlayer placed on at least one side of the polyester film, wherein thehard coat layer has a surface with irregularities, an interface betweenthe polyester film and the hard coat layer has irregularities, and thesurface of the hard coat layer has 3D surface roughness parametersincluding an arithmetical mean deviation of surface Sa of from 15 nm toless than 150 nm and a kurtosis of surface height distribution Sku offrom 1.5 to 5;(2) The hard-coated film of (1), wherein the interface between thepolyester film and the hard coat layer has irregularities on thepolyester film side, and projections of the irregularities on thepolyester film side coincide with depressions of the hard coat surfaceprofile in the thickness direction;(3) The hard-coated film of (1) or (2), wherein the hard coat layer is athermally hardened layer;(4) The hard-coated film of any one of (1) to (3), wherein the polyesterfilm contains ultraviolet ray-absorbing agents;(5) The hard-coated film of any one of (1) to (4), wherein theirregularities of the hard coat layer are formed without the aid ofparticles in the hard coat layer and the polyester film;(6) The hard-coated film of any one of (1), (3), (4), and (5), whereinthe interface between the polyester film and the hard coat layer hasirregularities on the polyester film side, projections of theirregularities on the polyester film side coincide with projections ofthe hard coat surface profile in the thickness direction, and thehard-coated film has a heat shrinkage ratio of at most 0.8% at 150° C.for 30 minutes in at least one direction;(7) The hard-coated film of any one of (1) to (6), wherein the hard coatlayer surface has an average Δa of from 0.2 degrees to 1.0 degree,wherein the average Δa is calculated from the formula Δa=(Δa1+Δa2)/2,wherein Δa1 and Δa2 are arithmetical mean slope angles of the hard coatlayer surface in two directions perpendicular to each other,respectively;(8) The hard-coated film of any one of (1) to (7), wherein the hard coatlayer surface has an Sa2/Sa1 ratio of from 2 to 20, wherein Sa1 is thearithmetical mean deviation of surface (Sa) of the hard coat layersurface, and Sa2 is the arithmetical mean deviation of surface (Sa) ofthe interface between the polyester film and the hard coat layer,concerning the 3D surface roughness parameters;(9) The hard-coated film of any one of (1) to (8), wherein Sku of thehard coat layer is from 1.5 to 3;(10) The hard-coated film of any one of (1) to (9), wherein thehard-coated film has a haze of less than 3%;(11) An antireflection film, including: the hard-coated film of item(1); and a low-refractive-index layer with a refractive index of at most1.45 that is formed on the hard coat layer of the hard-coated film,optionally with a high-refractive-index layer with a refractive index ofat least 1.55 interposed between the hard coat layer and thelow-refractive-index layer;(12) The antireflection film of (11), wherein it has a haze of less than4% and a transmittance of at most 5% at a wavelength of 380 nm;(13) A method for producing a hard-coated film, including the steps of:applying a hard coating composition to a polyester film afterlongitudinal stretching during a polyester film forming process; thenslightly stretching the film 1.1 to 1.8 times in the transversedirection, while continuously feeding the film to a tenter; then furtherstretching the film 2.5 to 3.5 times; and then relaxing the film by 3%to 7% in the transverse direction, while the hard coat layer isthermally hardened; and(14) The method of (13), further including the step of relaxing the filmby 1.5% to 15% in the longitudinal direction and/or the transversedirection at 200° C. to 240° C. after the relaxation by 3% to 7%.

Effects of the Invention

The hard-coated film and the antireflection film of the invention eachhaving any of the features described above exhibit reduced interferenceiris patterns and reduced coloration irregularity of surface reflectedlight after the antireflection treatment. Therefore, when they are usedfor display applications or the like, a high level of clear viewproperties are provided, and when used for a front face filter of aplasma display, they each have the effect of preventing reflection,provide a high level of clear view properties, keep images sharp, andprevent screen glittering.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the relationship between the irregularities of the hardcoat layer surface and the irregularities of the interface between PETand the hard coat layer, in which projections of the hard coat layersurface coincide with projections of the polyester film surface in theinterface with the hard coat layer.

FIG. 2 shows the relationship between the irregularities of the hardcoat layer surface and the irregularities of the interface between PETand the hard coat layer, in which depressions of the hard coat layersurface coincide with projections of the polyester film surface in theinterface with the hard coat layer.

FIG. 3 is a diagram schematically showing the arithmetical mean slopeangle (Δa) in an embodiment of the invention.

DESCRIPTION OF REFERENCE SYMBOLS

In the drawings, reference numeral 1 represents a hard coat surface and2 a polyester surface.

BEST MODE FOR CARRYING OUT THE INVENTION

The hard-coated film of the invention including a polyester film and ahard coat layer placed on at least one side of the polyester film or theantireflection film therewith is characterized in that the surface ofthe hard coat layer and the interface between the polyester film and thehard coat layer each have irregularities, the surface of the hard coatlayer has 3D surface roughness parameters including an arithmetical meandeviation of surface Sa of from 15 nm to less than 150 nm and a kurtosisof surface height distribution Sku of from 1.5 to 5. The polyester ofthe polyester base film in the invention may be polyethyleneterephthalate, polyethylene naphthalate, polypropylene terephthalate,polybutylene terephthalate, polypropylene naphthalate, or a combinationof two or more of the above. The polyester may also be a copolymer ofany of these monomers and any other dicarboxylic acid or diol component.In this case, the polyester film is preferably a crystal-oriented filmwith a crystallinity of 25% or more, more preferably 30% or more, evenmore preferably 35% or more. If the crystallinity is less than 25%,dimensional stability or mechanical strength may tend to beinsufficient. The crystallinity may be determined by a density gradientmethod (JIS K 7112 (1980)) or Raman spectroscopic analysis.

When the polyester described above is used, its intrinsic viscosity (thevalue measured in o-chlorophenol at 25° C. according to JIS K 7367) ispreferably from 0.4 to 1.2 dl/g, more preferably from 0.5 to 0.8 dl/g.

The polyester film used in the invention may be a composite film havinga laminated structure of two or more layers. For example, such acomposite film may be a composite film including an inner layer partsubstantially free of particles and a surface layer part containingparticles. The inner layer part and the surface layer part may be madeof chemically different polymers or the same polymer. When the film ofthe invention is for use in display antireflection films, the featurethat the polyester film is free of particles and so on is preferred inview of optical properties, because an internal scattering-inducedincrease in haze or the like can be prevented.

In the invention, the polyester film with the hard cost layer providedthereon is preferably crystal-oriented by biaxial stretching so that thethermal stability of the film, specifically the dimensional stability orthe mechanical strength, can be sufficient and a high level of flatnesscan be provided. The film crystal-oriented by biaxial stretching isintended to include a film that shows a biaxial orientation pattern in awide angle X-ray diffraction analysis and is produced by a processincluding the steps of stretching a non-crystal-oriented thermoplasticresin film 2.5 to 5 times in the longitudinal direction and/or thetransverse direction and then heat-treating the film to complete crystalorientation.

The thickness of the polyester film used in the invention may be from 10to 500 μm, preferably from 20 to 300 μm in view of mechanical strength,handling or the like, while it may be appropriately selected dependingon the use of the hard-coated film of the invention. When used fordisplay antireflection films, the polyester film particularly preferablyhas a thickness of 75 to 200 μm.

The polyester film of the invention may contain various additives, resincompositions, crosslinking agents or the like, as long as the effects ofthe invention are not inhibited. Examples of such materials includeantioxidants, heat-resisting stabilizers, ultraviolet ray-absorbingagents, organic or inorganic particles (such as silica, colloidalsilica, alumina, alumina sol, kaolin, talc, mica, calcium carbonate,barium sulfate, carbon black, zeolite, titanium oxide, and metal fineparticles), pigments, dyes, antistatic agents, nucleus formation agents,acrylic resins, polyester resins, urethane resins, polyolefin resins,polycarbonate resins, alkyd resins, epoxy resins, urea resins, phenolresins, silicone resins, rubber resins, wax compositions, melaminecrosslinking agents, oxazoline crosslinking agents, methylolated oralkylolated urea crosslinking agents, acrylamide, polyamide, epoxyresins, isocyanate compounds, aziridine compounds, various silanecoupling agents, and various titanate coupling agents.

Particularly when used for plasma display antireflection films, thepolyester film preferably has an ultraviolet light interception functionand preferably contains an ultraviolet ray-absorbing agent so that a dyehaving a color correction or near-infrared light interception functionmay be used.

Preferred examples of the ultraviolet ray-absorbing agent includesalicylic acid-based compounds, benzophenone-based compounds,benzotriazole-based compounds, cyanoacrylate-based compounds,benzoxazinone-based compounds, and cyclic iminoester compounds.Benzoxazinone-based compounds are most preferred in view of color toneand ultraviolet light interception at 380 nm to 390 nm. One or more ofthese compounds may be used alone or in any combination. These compoundsare more preferably used in combination with a stabilizer such as ahindered amine light stabilizer (HALS) and an antioxidant.

Examples of benzoxazinone-based compounds (preferred materials) include2-p-nitrophenyl-3,1-benzoxazine-4-one,2-(p-benzoylphenyl)-3,1-benzoxazine-4-one,2-(2-naphthyl)-3,1-benzoxazine-4-one,2-2′-p-phenylenebis(3,1-benzoxazine-4-one), and2,2′-(2,6-naphthylene)bis(3,1-benzoxazine-4-one). The polyester basefilm may contain 0.5 to 5% by weight, preferably 1 to 5% by weight, ofany of these compounds.

In order to impart further improved light resistance, acyanoacrylate-based tetramer compound is preferably used in combinationtherewith. The base film preferably contains 0.05 to 2% by weight of acyanoacrylate-based tetramer compound. The cyanoacrylate-based tetramercompound is a compound based on a tetramer of cyanoacrylate, examples ofwhich include1,3-bis(2′cyano-3,3-diphenylacryloyloxy)-2,2-bis-(2′cyano-3,3-diphenylacryloyloxymethylpropane)and the like. When used in combination with this compound, theultraviolet ray-absorbing agent is preferably added in an amount of 0.3to 3% by weight to the base film.

When the ultraviolet ray-absorbing agent is added, the hard-coated filmof the invention and the antireflection film with the hard-coated filmeach preferably has a transmittance of 5% or less, more preferably 3% orless, at a wavelength of 380 nm, so that the base film, the dye, orpigment can be protected from ultraviolet rays particularly when thefilm is used as a plasma display component. The transmittance may bedetermined at a wavelength of 380 nm with a spectrophotometer U-3410(manufactured by Hitachi, Ltd.) equipped with an integrating sphere130-063 with a diameter of 60 mm (manufactured by Hitachi, Ltd.) and a10°-inclined spacer.

The hard-coated film of the invention preferably has a total lighttransmittance of 90% or more, more preferably 92% or more, even morepreferably 94% or more. If the total light transmittance is less than90%, the hard-coated film may inhibit the sharpness of images when itforms an antireflection film.

The hard-coated film of the invention includes a polyester film and ahard coat layer placed on at least one side of the polyester film andhaving a surface with irregularities, wherein the hard coat surface has3D surface roughness parameters including an arithmetical mean deviationof surface Sa of from 15 nm to less than 150 nm and a kurtosis ofsurface height distribution Sku of from 1.5 to 5.

The 3D surface roughness of the hard coat surface may be determined fromthe 3D surface profile of the hard coat surface obtained by measuringthe hard coat surface with a surface profiler SP-500 or SP-700(manufactured by Toray Engineering Co., Ltd., a system capable ofnon-destructively measuring interface shape and surface profile at thesame time) and a ×5 objective lens in WSI mode. The arithmetical meandeviation of surface Sa and the kurtosis of surface height distributionSku, which are 3D surface roughness parameters of the hard coat surfacedefined according to the invention, may be obtained by analyzing the 3Dsurface profile (measured with SP-500 or SP-700) with a nanoscale 3Dimage processing software SPIP™ (manufactured by Image Metrology A/S).

More specifically, the arithmetical mean deviation of surface Sa isobtained by extending two-dimensional Ra to three-dimensional level andmay be calculated by dividing, by the measured area, the volumesurrounded by a curve of surface shape and a mean surface, according tothe formula below. When the XY plane and the Z axis represent thehorizontal plane and the vertical direction, respectively, and when theheight at the k-th x and l-th y in the measured curve of surface shapeis expressed as z(xk,yl), the following formula is derived.

$\begin{matrix}{S_{a} = {\frac{1}{MN}{\sum\limits_{k = 0}^{M - 1}{\sum\limits_{l = 0}^{N - 1}{{{z\left( {x_{k},y_{l}} \right)} - \mu}}}}}} & \left\lbrack {{su}\; 1} \right\rbrack\end{matrix}$

The term μ is a mean surface calculated from the following formula.

$\begin{matrix}{\mu = {\frac{1}{MN}{\sum\limits_{k = 0}^{M - 1}{\sum\limits_{l = 0}^{N - 1}{z\left( {x_{k},y_{l}} \right)}}}}} & \left\lbrack {{su}\; 2} \right\rbrack\end{matrix}$

The kurtosis of surface height distribution Sku is a measure of thesharpness of the curve of surface shape for characterizing the spread ofthe surface height distribution and is defined by the following formula.

$\begin{matrix}{S_{ku} = {\frac{1}{{MNS}_{q}^{4}}{\sum\limits_{k = 0}^{M - 1}{\sum\limits_{l = 0}^{N - 1}\left\lbrack {{z\left( {x_{k},y_{l}} \right)} - \mu} \right\rbrack^{4}}}}} & \left\lbrack {{su}\; 3} \right\rbrack\end{matrix}$

Sq is a three-dimensional extension of two-dimensional Rq (RMS) andcorresponds to a standard deviation σ in statistics. Sq is aroot-mean-square deviation obtained by dividing, by the measured area,the volume of the portion between the mean surface and the curvedsurface calculated by squaring the distance between the curve of surfaceshape and the mean surface and then calculating the square root of thequotient.

$\begin{matrix}{S_{q} = \sqrt{\frac{1}{MN}{\sum\limits_{k = 0}^{M - 1}{\sum\limits_{l = 0}^{N - 1}\left\lbrack {{z\left( {x_{k},y_{l}} \right)} - \mu} \right\rbrack^{2}}}}} & \left\lbrack {{su}\; 4} \right\rbrack\end{matrix}$

When Sku=3, a normal distribution is provided, and as this valuedecreases, the surface height distribution becomes a smooth shape, whilean increase in this value means that the projection becomes sharp.

Concerning the 3D surface roughness parameters of the surface of thehard coat layer according to the invention, the arithmetical meandeviation of the surface Sa is 15 nm or more and less than 150 nm,preferably from 20 nm to 100 nm, more preferably from 30 nm to 85 nm,and the kurtosis of surface height distribution Sku is from 1.5 to 5,preferably from 1.5 to 3, more preferably from 1.5 to 2.5. If Sa is lessthan 15 nm, the hard coat layer surface is so smooth that after theantireflection treatment, light reflected from the surface can sufferfrom color heterogeneity, or reflection of external light such asfluorescent lamp light can increase, which may lead to a defectiveappearance or a reduction in clear view properties. If Sa is 150 nm ormore, reflected light can be scattered by the hard coat surface so thatreflection of external light such as fluorescent lamp light can beeffectively reduced, but sharpness can be reduced due to clouding orsignificant scattering of transmitted images, and screen glittering canbe significant.

Theoretically, Sku does not become less than 1. If Sku is more than 5,the surface would have sharp projections in a scattered manner so thatvisible color heterogeneity or screen glittering can be caused byreflected light after the antireflection treatment, which may lead to adefective appearance. If Sku is less than 1.5, the projection shapewould be smooth so that reflection of external light or fluorescent lamplight may tend to be increase.

The hard coat surface profile (Sa and Sku) according to the invention ismost preferably achieved using a method of providing the hard coat layerduring the process of preparing the polyester film, because ofcleanliness and cost effectiveness and because the hard coat layersurface and the interface between the polyester film and the hard coatlayer can be shaped at the same time by such a method. According to sucha method, the surface irregularities of the hard coat layer can becontrolled in such a manner that irregularities of the interface betweenthe polyester film and the hard coat layer are formed and reflected.Specifically, the surface profile may be controlled by optimizing thecoating liquid viscosity, the stretching process in the transversedirection after the hard coat layer coating, the thermal history of thehard coat layer-hardening process, or the relaxation process after thehard coat layer-hardening process.

When the interface between the hard coat layer and the polyester filmhas irregularities, an interference iris pattern can be reduced, whichwould otherwise be caused by interference of reflected light from thehard coat layer surface and the hard coat layer/base interface inconventional technologies. Specifically, the projections present in theinterface allows the segmentation of the interface area from which lightbeams are reflected with the same optical path difference, so that aninterference iris pattern is divided into segments at an invisibledomain level, which reduces the interference iris pattern. When thisstructure is formed, screen glittering can also be reduced.

The projections (bumps) of the irregularities of the interface betweenthe hard coat layer and the polyester film preferably has a height offrom 0.3 μm to 2 μm, more preferably from 0.3 μm to 1 μm, even morepreferably from 0.4 μm to 0.7 μm.

A projection height of more than 2 μm is not preferred, because such aheight can make the hard coat layer surface too rough or can cause thetransmitted image to glitter. As used herein, the term “projectionheight” refers to the maximum height Rz of an interface shape curve (JISB 0601:'01).

According to the invention, the hard coat layer surface has specific Saand Sku values as described above. Such irregularities of the hard coatlayer surface is effective not only in reducing the interference irispattern but also in reducing coloration of reflected light from theantireflection layer further placed on the hard coat layer surface,reducing coloration irregularity, and reducing reflection of externallight without screen glittering. The projections present in the hardcoat surface are effective in producing fine unevenness in the thicknessof the antireflection layer so that the intensity of reflected light inthe visible light range can be flattened and the wavelength dependencecan be reduced.

In an embodiment of the invention, if necessary, a polyester-basedadhesive layer, an acrylic adhesive layer, a polyurethane-based adhesivelayer, or the like may be interposed between the polyester film and thehard coat layer. In a preferred aspect of the invention, however, thepolyester base film and the hard coat layer are strongly bonded to eachother with no adhesive layer interposed therebetween so that theadhesion can be maintained under moisture or heat and that interferenceiris patterns can be reduced.

In the invention, the interface between the hard coat layer and thepolyester film may have irregularities on the polyester film surface,and the hard coat surface profile may have depressions immediately aboveprojections of the irregularities in the cross-sectional direction.Alternatively, projections of the interface may coincide withprojections of the hard coat layer surface in a pattern contrary to theabove. As used herein, the term “cross-sectional direction” refers to adirection perpendicular to the film surface.

Specifically, FIG. 1 shows a state where in the cross-sectionaldirection, depressions of the curve of surface roughness of thehard-coated film coincide with projections of the curve of roughness ofthe interface between the polyester film and the hard coat layer, andFIG. 2 shows a pattern contrary thereto.

The state where depressions of the curve of surface roughness of thehard-coated film coincide with projections of the curve of roughness ofthe interface between the polyester film and the hard coat layer cannotbe achieved by conventional techniques such as conventional addition ofparticles, conventional shape-transfer methods, and conventional coatingmethods. It has been found that the state can be achieved by the methodof applying a coating liquid to form the hard coat layer during the filmforming process according to the invention as described herein and thatthe reverse pattern can also be formed by a direct extension of such atechnique.

Examples of methods for checking such a structure include a methodincluding the steps of cutting a cross-section from the film andobserving the cross-section with a microscope to obtain profile linesfrom the hard coat layer surface and from the interface between thepolyester film and the hard coat layer, and a method including the stepof measuring the curves of surface roughness and the interface roughnessat the same time with a surface profiler SP-500 or SP-700 (manufacturedby Toray Engineering Co., Ltd.). In view of measurement accuracy, thestructure is most preferably checked by the method using a surfaceprofiler SP-500 or SP-700 (manufactured by Toray Engineering Co., Ltd.,a system capable of non-destructively measuring interface shape andsurface profile at the same time).

The interface between the hard coat layer and the polyester filmaccording to the invention, which has irregularities, may be formed bythe method described below that includes applying a hard coatlayer-forming coating liquid to a thermoplastic film under conditionssuch that the surface of the film can be cracked during stretching ofthe film before stretch orientation completion and forming projectionson the interface in the stretching process.

Additionally, in order to achieve the hard coat surface profile (Sa andSku), a feature according to the invention, the transverse stretchingtemperature may be lowered so that the leveling capability of thenon-hardened coating film surface can be controlled after theapplication of the hard coat layer-forming coating liquid and until thecoating is hardened and so that the leveling capability can be reduced,and a heating leveling zone may be provided to increase the levelingcapability, so that the surface irregularities can be controlled.

In general, the thickness of the hard coat layer is preferably from 0.5μm to 30 μm, more preferably from 1 μm to 15 μm, while it may bedetermined depending on use. If the hard coat layer has a thickness ofless than 0.5 μm, it may be so thin that it may tend to have aninsufficient surface hardness and to be damaged, even when it issufficiently hardened. If it has a thickness of more than 30 μm, it maytend to curl during hardening, or the hardened film may tend to becracked by stress such as bending stress.

The hard-coated film having the structure described above may beproduced by the method described below.

The hard coat layer-forming composition to be placed on at least oneside of the polyester film typically includes an acrylic compound, aurethane compound, a urethane acrylate compound, a melamine compound, anorganic silicate compound, a silicone compound, a metal oxide, or thelike. In particular, a heat- or active ray-hardenable acrylic compoundis preferred, and a hardenable composition including a multi-functionalacrylate compound as a main component is preferred. The main componentpreferably makes up at least 50% by weight, more preferably at least 70%by weight of, the hard coat layer. The term “multi-functional acrylate”refers to a monomer, oligomer, or prepolymer having at least three (morepreferably at least four, even more preferably at least five)(meth)acryloyloxy groups per molecule (it should be noted that as usedherein, the term “ . . . (meth)acry . . . ” is an abbreviation for “ . .. acry . . . or . . . methacry . . . ”). Such a composition may includea compound produced by esterification of the hydroxyl groups of apolyhydric alcohol having three or more alcoholic hydroxyl groups permolecule with three or more molecules of (meth)acrylic acid.

Examples of such a compound that may be used include pentaerythritoltri(meth)acrylate, pentaerythritol tetra(meth)acrylate,dipentaerythritol tetra(meth)acrylate, dipentaerythritolpenta(meth)acrylate, dipentaerythritol hexa(meth)acrylate,trimethylolpropane tri(meth)acrylate, pentaerythritol triacrylatehexamethylene diisocyanate urethane prepolymer, pentaerythritoltriacrylate toluene diisocyanate urethane prepolymer, andpentaerythritol triacrylate isophorone diisocyanate urethane prepolymer.One or more of them may be used alone or in any combination.

The monomer, oligomer, or prepolymer having at least three(meth)acryloyloxy groups per molecule is preferably used in an amount of50 to 90% by weight, more preferably 50 to 80% by weight, based on thetotal amount of the hard coat layer-forming components.

The compound described above is preferably used in combination with anyother monofunctional or bifunctional acrylate for the purpose ofrelaxing the rigidity of the hard coat layer, reducing the contractionduring hardening, or adjusting the viscosity of the coating liquid. Anyradically-polymerizable monomer having one or two ethylenic unsaturateddouble bonds per molecule may be used without particular restrictions.

Examples of compounds having two ethylenic unsaturated double bonds permolecule that may be used include the following compounds:

(a) (meth)acrylate diesters of C₂ to C₁₂ alkylene glycol such asethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate,1,4-butanediol di(meth)acrylate, neopentylglycol di(meth)acrylate, and1,6-hexanediol di(meth)acrylate;

(b) (meth)acrylate diesters of polyoxyalkylene glycol such as diethyleneglycol di(meth)acrylate, triethylene glycol di(meth)acrylate,tetraethylene glycol di(meth)acrylate, dipropylene glycoldi(meth)acrylate, polyethylene glycol di(meth)acrylate, andpolypropylene glycol di(meth)acrylate;(c) (meth)acrylate diesters of polyhydric alcohol such aspentaerythritol di(meth)acrylate;(d) (meth)acrylate diesters of ethylene oxide adducts and propyleneoxide adducts of bisphenol A or hydrogenated bisphenol A, such as2,2′-bis(4-acryloxy-ethoxy-phenyl)propane and2,2′-bis(4-acryloxy-propoxy-phenyl)propane;(e) urethane (meth)acrylates having at least two (meth)acryloyloxygroups per molecule, which are produced by the reaction of a terminalisocyanate group-containing compound with an alcoholic hydroxylgroup-containing (meth)acrylate, wherein the terminal isocyanategroup-containing compound is produced by the pre-reaction of adiisocyanate compound with a compound containing at least two alcoholichydroxyl groups; and(f) epoxy (meth)acrylates having at least two (meth)acryloyloxy groupsper molecule, which are produced by the reaction of a compound having atleast two epoxy groups per molecule with acrylic or methacrylic acid.

Examples of compounds having one ethylenic unsaturated double bond permolecule that may be used include methyl (meth)acrylate, ethyl(meth)acrylate, n-propyl or isopropyl (meth)acrylate, n-, sec-, ortert-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl(meth)acrylate, stearyl (meth)acrylate, methoxyethyl (meth)acrylate,ethoxyethyl (meth)acrylate, hydroxyethyl (meth)acrylate, polyethyleneglycol mono(meth)acrylate, polypropylene glycol mono(meth)acrylate,glycidyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate,N-hydroxyethyl(meth)acrylamide, N-vinylpyrrolidone,N-vinyl-3-methylpyrrolidone, and N-vinyl-5-methylpyrrolidone. One ormore of these monomers may be used alone or in any combination.

The monomer or monomers having one or two ethylenic unsaturated doublebonds per molecule are preferably used in an amount of 10 to 40% byweight, more preferably 20 to 40% by weight, based on the total amountof the hard coat layer-forming components. The acrylic oligomer is acompound having an acrylic resin skeleton and a reactive acrylic groupbonded thereto, such as polyester acrylate, urethane acrylate, epoxyacrylate, and polyether acrylate, and a compound having a rigid skeletonsuch as melamine or isocyanuric acid and an acrylic group bonded to theskeleton may also be used.

The coating composition composed of these materials preferably has aviscosity of 1000 to 5000 mPa·s (25° C.) or a viscosity of 50 to 200mPa·s during heating (100° C.). Particularly when the viscosity is from50 to 200 mPa·s during heating (100° C.), the hard coat layer surfaceprofile can be easily controlled.

If the coating liquid has a viscosity of less than 50 mPa·s duringheating (100° C.), its fluidity is so high that the surface cannot beformed in such a manner that the irregularities of the interface betweenthe hard coat layer and the base film, so that it may be smoothed. Ifthe coating liquid has a viscosity of more than 200 mPa·s during heating(100° C.), its fluidity is so low that a long leveling time may berequired to produce the desired surface profile so that the productivitymay be reduced. In the invention, the viscosity of the coating liquidmay be measured with an E-type viscometer, and when the coatingcomposition contains a volatile substance at 100° C. or lower, theviscosity is a value obtained by measuring the viscosity of a residueresulting from heating the coating composition in an open system at 100°C. for 10 minutes.

In the invention, if necessary, a reactive diluent may also be used. Thereactive diluent is a material that serves as a coating compositionmedium to reduce the viscosity in the coating process and has a groupreactive with a monofunctional or multifunctional acrylic oligomer toserve as a co-reactive component for the coating film by itself.

Examples of the acrylic oligomer, the reactive diluent, and the like maybe found in Shinzo Yamashita and Tosuke Kaneko (ed.), “CrosslinkingAgent Handbook,” published by Taiseisha, Ltd. (1981), pages 267 to 275and pages 562 to 593. Examples of commercially-available curablemultifunctional acrylic coating compositions that may be used includeDiabeam (registered trademark) series manufactured by Mitsubishi RayonCo., Ltd., Dinacol (registered trademark) series manufactured by NAGASE& COMPANY, Ltd., NK Ester (trade name) series manufactured byShin-Nakamura Chemical Co., Ltd., UNIDIC (trade name) seriesmanufactured by Dainippon Ink & Chemicals, ARONIX (registered trademark)series manufactured by Toagosei Co., Ltd., BLENMER (registeredtrademark) series manufactured by NOF CORPORATION, KAYARAD (trade name)series manufactured by NIPPON KAYAKU Co., Ltd., and LIGHT ESTER(registered trademark) and LIGHT ACRYLATE (registered trademark) seriesmanufactured by Kyoeisha Chemical Co., Ltd.

In the invention, an application conditioner, an antifoaming agent, athickener, an antistatic agent, inorganic particles, organic particles,an organic lubricant, an organic polymer compound, an ultravioletray-absorbing agent, a light stabilizer, a dye, a pigment, a stabilizer,or the like may be used as a modifier for the hard coat layer. Any ofthese materials may be used as a component of a coating layercomposition to form the hard coat layer and can modify the properties ofthe hard coat layer depending on use, as long as the reaction by heatingor active rays is not reduced.

In the invention, for example, the hard coating composition may behardened by a method of applying ultraviolet rays as active rays, ahigh-temperature heating method, or the like. When these methods areused, a photopolymerization initiator, a thermal polymerizationinitiator, or the like is preferably added to the hard coatingcomposition.

Examples of photopolymerization initiators that may be used includecarbonyl compounds such as acetophenone, 2,2-diethoxyacetophenone,p-dimethylacetophenone, p-dimethylaminopropyophenone, benzophenone,2-chlorobenzophenone, 4,4′-dichlorobenzophenone,4,4′-bisdiethylaminobenzophenone, Michler's ketone, benzyl, benzoin,benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether,methyl benzoyl formate, p-isopropyl-α-hydroxyisobutylphenone,α-hydroxyisobutylphenone, 2,2-dimethoxy-2-phenylacetophenone,1-hydroxycyclohexyl phenyl ketone; and sulfur compounds such astetramethylthiuram monosulfide, tetramethylthiuram disulfide,thioxanthone, 2-chlorothioxanthone, and 2-methylthioxanthone. One ormore of these photopolymerization initiators may be used alone or in anycombination. A peroxide compound such as benzoyl peroxide, di-tert-butylperoxide, or the like may be used as the thermal polymerizationinitiator.

The photopolymerization initiator or the thermal polymerizationinitiator is appropriately used in an amount of 0.01 to 10 parts byweight, based on 100 parts by weight of the hard coat layer-formingcomposition. When electron beams or gamma rays are used for hardening,addition of the polymerization initiator is not necessarily required.Also when thermal hardening at a high temperature of 200° C. or higheris performed, addition of the thermal polymerization initiator is notnecessarily required.

In order to prevent unnecessary thermal polymerization duringmanufacturing or to prevent a dark reaction during storing, a thermalpolymerization preventing agent such as hydroquinone, hydroquinonemonomethyl ether, or 2,5-tert-butylhydroquinone is preferably added tothe hard coat layer-forming composition used in the invention. Thethermal polymerization preventing agent is preferably added in an amountof 0.005 to 0.05% by weight, based on the total weight of the hard coatlayer-forming composition.

In the invention, an isocyanate compound or a melamine-basedcrosslinking agent is preferably added to the coating composition toform the hard coat layer so that the hard coat layer can be directlybonded to the polyester film. Known isocyanate compounds may be used,examples of which include monomers, dimers, or oligomers of 2,4- and/or2,6-tolylenediisocyanate, 4,4′-diphenylmethane diisocyanate (abbreviatedas MDI), polymeric MDI, 1,5-naphthylenediisocyanate,tolidinediisocyanate, 1,6-hexamethylenediisocyanate (abbreviated asHDI), trimethyl hexamethylene diisocyanate, isophorone diisocyanate,xylylene diisocyanate (abbreviated as XDI), hydrogenated XDI,hydrogenated MDI, lysinediisocyanate, triphenylmethane triisocyanate,and tris(isocyanatophenyl)thiophosphate. One or more of them may be usedalone or in any combination. While the melamine-based crosslinking agentmay be of any type, melamine, methylolated melamine derivatives producedby condensation of melamine and formaldehyde, partially or completelyetherified compounds produced by the reaction of methylolated melaminewith lower alcohol, or any mixture thereof may be used. Themelamine-based crosslinking agent to be used may be a monomer, a dimer,a condensation oligomer, or any mixture thereof.

The lower alcohol to be used for the etherification may be methylalcohol, ethyl alcohol, isopropyl alcohol, n-propyl alcohol, n-butanol,isobutanol, or the like. The melamine-based crosslinking agent may havean imino group, a methylol group, or an alkoxymethyl group such asmethoxymethyl or butoxymethyl as a functional group in the molecule andmay be an imino group-type methylated melamine, a methylol group-typemelamine, a methylol group-type methylated melamine, a completealkylation-type methylated melamine, or the like. In particular,methylolated melamine and complete alkylation melamine are preferred inview of adhesion. The content of the isocyanate compound or themelamine-based crosslinking agent in the solids of the hard coat-formingcoating composition is preferably, but not limited to, from 2 to 40% byweight, more preferably from 5 to 30% by weight, in view of a balancebetween adhesion and hardness.

In order to enhance the hardening of melamine, an acid catalyst ispreferably used in combination with the melamine-based crosslinkingagent. The acid catalyst that may be used is preferablyp-toluenesulfonic acid, dodecylbenzenesulfonic acid,dimethylpyrophosphoric acid, styrenesulfonic acid, or any derivativethereof (such as a block agent (dimethylethanolamine or the like)adduct). The acid catalyst is preferably added in an amount of 0.05 to10% by weight, more preferably 1 to 5% by weight (on a solid basis),based on the amount of the melamine crosslinking agent. When themelamine-based crosslinking agent is added, it is particularly preferredthat the coating composition should include a multifunctional acrylatehaving at least one hydroxyl group, in terms of improving the adhesion.

In the process of forming the hard coat layer according to theinvention, a leveling agent is preferably used to moderately smooth thehard coat layer surface. Typical leveling agents include siliconeleveling agents, acrylic leveling agents, fluoride leveling agents, andso on. When only smoothness is required, addition of a small amount of asilicone leveling agent is effective. Such a silicone leveling agentpreferably has a polydimethylsiloxane main skeleton to whichpolyoxyalkylene groups are added (for example, SH 190 manufactured byToray Dow Corning Silicone Corporation).

When a laminated film is further provided on the hard coat layer, thecoatability and adhesion of the laminated film are required not to beinhibited. In such a case, acrylic leveling agents are preferably used.Such acrylic leveling agents preferably used include ARUFON-UP1000series, UH2000 series, and UC3000 series (trade names) manufactured byToagosei Co., Ltd. The content of the leveling agent added to the hardcoat layer-forming composition is preferably from 0.01 to 5% by weight.

The most preferred mode of the formation of projections on the interfacebetween the polyester film and the hard coat layer and on the hard coatlayer surface is specifically described below.

An ultraviolet ray-absorbing agent-containing polyester materialsubstantially free of projection-forming particles is subjected to meltextrusion and cast on a mirror surface drum with a staticelectricity-applying system so that it is formed into a sheet. The sheetis stretched 3 to 4.5 times in the longitudinal direction. In thisprocess, heating stretching is performed with a radiation heater so thatthe refractive index in the longitudinal direction can be from 1.62 to1.68 according to abbe method and that the crystallinity of the hardcoating composition-receiving side can be from about 11 to about 25%according to Raman method.

A hard coating composition prepared with a multifunctional acrylate, abifunctional or trifunctional acrylate, a melamine-based crosslinkingagent and a hardening catalyst therefor, a leveling agent, and so on isapplied in a thickness of about 10 to about 20 μm to the hard coatingcomposition-receiving surface of the film. The coated film iscontinuously introduced into a tenter and stretched in the transversedirection, while its end is held with a clip. In this tenter, the filmis preheated to 60 to 80° C. and then slightly stretched 1.1 to 1.8times in the transverse direction at 70 to 85° C. The slight stretchingforms fine cracks on the surface of the film that is crystal-oriented inthe longitudinal direction. A part of the hard coating compositioninfiltrates into the cracks. The hard coat layer surface formsdepressions at sites where the coating composition infiltrates. Theinfiltration parts improve the crystallinity of the PET around them.After the slight stretching, the coated film is further stretched 2.5 to3.5 times in the transverse direction at 85 to 100° C., so that the hardcoating composition-infiltrating parts with improved crystallinity formgently raised projections. The hard coat layer surface forms gentledepressions immediately above the projections of the interface.Therefore, the depressions of the hard coat surface are formed inresponse to and immediately above the interface projections. The film isthen continuously introduced into a heat treatment zone at 200 to 235°C. so that the hard coat layer is cured by heating, while the film isrelaxed by 3 to 7% in the transverse direction. After the heathardening, the film is further heat-treated under tension at 220 to 240°C. so that the orientation and crystallization of the polyester basefilm is completed. The hard-coated film obtained by this method has ahard coat surface Sa of about 15 to about 70 nm and has a pattern inwhich each projection of the interface and each depression of the hardcoat surface coincide with each other in the thickness direction.

In order to further increase Sa, the film after the heat hardening maybe relaxed by 1.5 to 15% in total in the longitudinal direction and/orthe transverse direction at 200 to 235° C. so that it can have Sa ofabout 50 to about 200 nm. The control of the relaxation rate allows Sato fall within the range according to the invention. When the method ofincreasing Sa by relaxation is used after the hardening of the hard coatlayer, projections of the interface between the polyester base film andthe hard coat layer and projections of the hard coat layer surface canbe configured to coincide with each other in the thickness direction.

The relaxation after the hardening of the hard coat layer allows thepolyester base film to shrink so that the projections are furtherraised, and, consequently, depressions of the hard coat layerimmediately above the projections are raised and converted intoprojections. Therefore, when the method of increasing Sa is used, therelationship between the interface structure and the surface structurecan be reversed with Sa and Sku falling within the range.

In the resulting surface profile, irregularities of the base film andthe hard coat layer are formed substantially without the aid ofparticles. Therefore, the surface profile can be free fromparticle-induced light scattering or substantially free from screenglittering. When depressions of the hard coat layer are formedimmediately above projections of the interface, respectively, externallight reflection can be effectively and significantly reduced,particularly in the normal direction, with no loss of image sharpnessand with no screen glittering. On the other hand, when projections ofthe hard coat layer surface are formed immediately above projections ofthe interface, respectively, the increase in Sa is synergisticallyeffective, so that reflection of strong external light such asfluorescent light can be effectively and highly reduced and thatsufficient relaxation can reduce the heat shrinkage ratio at 150° C. for30 minutes to 0.8% or less, which is particularly preferred, because thedimensional stability is improved against heating in the subsequentantireflection process or the like.

The hard-coated film obtained by the most preferred method describedabove has irregularities on the interface and on the hard coat surface.Concerning Sa defined above, Sa (Sa1) of the hard coat layer surface isfrom 15 nm and less than 150 nm, and the ratio of Sa (Sa2) of theinterface to Sa1 (Sa2/Sa1) should be from 2 to 20, preferably from 5 to15, in view of a balance between image sharpness and screen glittering.

In view of a balance between antireflection and screen glittering, thearithmetical mean slope angle (Δa) of the hard coat layer surfacedefined below should be from 0.2 to 1.0 degree, preferably from 0.3 to0.7 degrees. In the invention, the arithmetical mean slope angle (Δa) ofthe hard coat layer surface may be determined from the 3D surfaceprofile of the hard coat surface obtained by measuring the hard coatsurface with a surface profiler SP-500 or SP-700 (manufactured by TorayEngineering Co., Ltd., a system capable of non-destructively measuringinterface and surface profiles at the same time) and a ×5 objective lensin WSI mode. Curved surfaces are measured in two directionsperpendicular to each other by 3D surface profile measurement,respectively. A measured curve obtained from each measured curvedsurface is segmented at regular intervals in the lateral direction(x-axis direction). The absolute value of the slope (angle) of the linebetween the starting and ending points of the measured curve in eachsegment is obtained. The average (Δa1, Δa2) of the values obtained overthe measured curves is further averaged (Δa=(Δa1+Δa2)/2). FIG. 3schematically shows the process for determining Δa. In general, Δa maybe calculated from the formula below. When the XY plane and the Z axisrepresent the horizontal plane and the vertical direction, respectively,and when the height at the k-th x and l-th y in the measured surfaceshape curve is expressed as z(xk,yl), the following formula is derived.

$\begin{matrix}{{\Delta\; a} = {\frac{1}{MN}{\sum\limits_{k = 0}^{M - 1}{\sum\limits_{l = 0}^{N - 1}\left\{ {\tan^{- 1}{\frac{{z\left( {x_{k + 1},y_{l}} \right)} - {z\left( {x_{k},y_{l}} \right)}}{x_{k + 1} - x_{k}}}} \right\}}}}} & \left\lbrack {{su}\; 5} \right\rbrack\end{matrix}$

If the arithmetical mean slope angle (Δa) of the surface is less than0.2 degrees, images reflected from the surface can be clearly visibleand undesirably reduce the clear view properties. If the arithmeticalmean slope angle (Δa) of the surface is more than 1.0 degrees, thetransmitted image can cause glittering, or white blur of the image canoccur, which is not preferred.

The arithmetical mean slope angle of the surface is an index of thedegree of diffused reflection on the surface. When the arithmetical meanslope angle Δa is 0 degrees, the surface can produce mirror reflection,and the reflected image is clearly visible. As the arithmetical meanslope angle Δa increases, diffused reflection increases, so that thereflected image becomes blurred. As the arithmetical mean slope angle Δafurther increases, multiple reflections can occur so that white blur ofthe image can be caused by light scattering. The arithmetical mean slopeangle Δa is set within the desired range so that the reflected image canbe slightly shifted and superimposed on the specularly reflected imageto form a blurred image.

The haze value of the hard-coated film of the invention should be lessthan 3%, preferably 2% or less, more preferably 1% or less, according toJIS K 7136. If the haze value is 3% or more, the clear view propertiesor the sharpness of the transmitted image may be reduced.

The haze may be controlled by the stretching temperature during the filmproduction. The haze may be reduced by lowering the stretchingtemperature, while it may be increased by raising the stretchingtemperature, so that the haze may be set in the range by controlling thestretching temperature.

The hard-coated film of the invention is highly productive, because thehard coat layer can be formed at once in the film forming process. Thehard-coated film of the invention produced as described above has highsurface hardness, high abrasion resistance, and high adhesion betweenthe hard coat layer and the base film with no adhesion-facilitatinglayer interposed therebetween. The hard-coated film of the inventionproduced as described above is also reduced in interference iris patternand has a high level of clear view properties. Therefore, thehard-coated film of the invention finds a wide range of uses and isparticularly suitable for use as a display antireflection filmsubstrate, a touch panel substrate, or the like.

The hard coat layer-forming coating composition may be applied usingvarious coating methods such as reverse coating, gravure coating, rodcoating, bar coating, die coating, and spray coating.

The heat required for thermal hardening of the hard coat layer may beprovided by heating air or an inert gas to a temperature of 140° C. orhigher with a steam heater, an electric heater, an infrared heater, or afar infrared heater and blowing the heated air or inert gas to the basefilm or the coating film through a slit nozzle. In particular, the heatis preferably provided by air heated at 200° C. or higher, morepreferably by nitrogen heated at 200° C. or higher, so that highhardening rate can be achieved.

The hard-coated film of the invention may be bonded to variousfunctional films by various methods before use. A pressure-sensitiveadhesive layer or an electrically-conductive layer may also be placed onthe other side of the hard-coated film.

For example, the other side of the hard-coated film of the inventionopposite to the hard coat layer may be bonded to a counterpart memberwith various pressure-sensitive adhesives so that the function of thehard coat layer such as abrasion resistance or scratch resistance may beimparted to the counterpart member before use. In this case, thepressure-sensitive adhesive to be used may be a rubber-based, acrylic,silicone-based, or polyvinyl ether-based pressure-sensitive adhesive(adhesive).

Pressure-sensitive adhesives-fall into two broad categories: solventtype pressure-sensitive adhesives and solvent-free typepressure-sensitive adhesives. Solvent type pressure-sensitive adhesivesare excellent in drying characteristics, productivity and processabilityand therefore dominant even now. In recent years, however, they havebeen being replaced by solvent-free type pressure-sensitive adhesives inview of environmental pollution, energy saving, resource conservation,safety, or the like. It is particularly preferred to use an activeray-hardenable pressure-sensitive adhesive that can be hardened inseconds by active ray irradiation and provide advantageous propertiessuch as flexibility, adhesion, and chemical resistance.

Examples of active ray-curable acrylic pressure-sensitive adhesivesinclude, but are not limited to, those found in “Adhesive Data Book,”edited by The Adhesion Society of Japan and published by The NikkanKogyo Shimbun, Ltd., 1990, pages 83 to 88. Commercially availableexamples of multifunctional ultraviolet-curable acrylic coatingcompositions include, but are not limited to, XY (trade name) seriesmanufactured by Hitachi Kasei Polymer Co., Ltd., Hirock (trade name)series manufactured by Toho Chemical Industry Co., Ltd., Three Bond(registered trademark) series manufactured by ThreeBond Co., Ltd.,Arontite (registered trademark) series manufactured by Toagosei Co.,Ltd., and Cemerock Super (registered trademark) serried manufactured byCemedine Co., Ltd.

When this type of adhesive is applied to a general biaxially-orientedpolyester film, insufficient adhesion is provided. Various types ofprimer treatment such as the deposition of an acrylic resin film, apolyester resin film, a urethane resin film, or the like can improve theadhesion between the polyester film and the pressure-sensitive adhesivelayer.

In the invention, the hard coat layer may be formed on one side, and aprimer layer may be formed on the other side to improve the adhesion tothe pressure-sensitive adhesive layer. It will be understood that theprocess of forming the primer layer may include coating of the backsurface when a coating liquid containing a thermally-hardenablecomposition for forming the hard coat layer is applied to the frontsurface; drying the coating; and optionally stretching.

The hard-coated film of the invention may be used for an antireflectionfilm of a plasma display or the like. In this case, it is preferablyused after a method for reducing the reflectance of the surface thatincludes providing a low-refractive-index layer with a refractive indexof 1.45 or less on the hard coat layer or providing ahigh-refractive-index layer with a refractive index of 1.55 or more onthe hard coat layer and then providing a low-refractive-index layer witha refractive index of 1.45 or less thereon, while it may be used as itis.

The high-refractive-index layer is preferably, but not limited to, alayer with a refractive index of about 1.55 to about 1.70 and athickness of 0.03 to 0.15 μm. Such a high-refractive-index layer may beobtained by dispersing metal compound fine particles into a bindercomponent. The binder component may be, but not limited to, ageneral-purpose resin such as a polyester, acrylic, urethane, or epoxyresin or the hard coat component according to the invention. The metalcompound particles per se have a relatively high refractive index.Examples of metal compound particles that may be used includetin-containing antimony oxide particles, zinc-containing antimony oxideparticles, tin-containing indium oxide particles, zinc oxide/aluminumoxide particles, antimony oxide particles, titanium oxide particles, andzirconium oxide particles. Compounds capable of imparting an antistaticfunction are more preferred, and, therefore, tin-containing indium oxideparticles are particularly preferred. The metal compound particlespreferably have an average primary particle size (a sphere-equivalentsize as measured by BET method) of 0.5 μm or less, more preferably 0.001to 0.3 μm, in order to maintain transparency. In order to improve theelectrical conductivity, an organic electrically-conductive materialsuch as polypyrrole, polyaniline, or polythiophene may be added to themetal compound.

The low-refractive-index layer preferably has a refractive index ofabout 1.30 to about 1.45 and a thickness of about 0.01 to about 0.15 μm.Known materials may be used to form the low-refractive-index layer, andfluorides or perfluoroalkyl group-containing compounds are preferablyused. The material may also be prepared by charging hollow fineparticles into binder resin. For example, such hollow particles aredescribed in published documents such as JP-A No. 2001-233611 and J. AM.Chem. Soc. 2003, 125, 316-317.

The antireflection film obtained by the above method preferably has ahaze of 4% or less and a transmittance of 5% or less at a wavelength of380 nm. If the transmittance at a wavelength of 380 nm is more than 5%,a near infrared light-intercepting dye or a polyester base film used asa component of a filter may be degraded during long-term use. Thisfeature may be achieved by adding an ultraviolet ray-absorbing agent tothe polyester base material, but any other method such as addition of anultraviolet ray-absorbing agent to the pressure-sensitive adhesive layermay also be used. If the haze of the antireflection film is more than4%, image sharpness may be affected. Therefore, the hard-coated film andthe high-refractive-index layer or the low-refractive-index layer formedthereon should keep the haze as low as possible.

Examples of coating methods include, but are not limited to,micro-gravure coating, gravure coating, micro-gravure reverse coating,gravure reverse coating, die coating, comma coating, kiss coating,capillary coating, and wire bar coating. In particular, micro-gravurecoating or micro-gravure reverse coating is preferred, because of itshigh coating thickness accuracy.

Characterization Methods and Effect Evaluation Methods

The methods described below are used for characterization and effectevaluation in the invention.

(1) Measurement of 3D Surface Profile, Arithmetical Mean Deviation ofSurface Sa (Sa1 and Sa2), Kurtosis of Surface Height Distribution Sku,Arithmetical Mean Slope Angle Δa, Shape of Interface between PolyesterFilm and Hard Coat Layer, and Interface Projection Height

The hard coat surface roughness is determined from the 3D surfaceprofile of the hard coat surface obtained by measuring the hard coatsurface with a surface profiler SP-500 (manufactured by TorayEngineering Co., Ltd.) equipped with a standard camera and a ×5objective lens in WSI mode. The data obtained by this measurement has avisual field size of 0.80 mm×0.72 mm, an in-plane resolution of 1.6 μm,and a height resolution of 1 nm.

The arithmetical mean deviation of surface Sa and the kurtosis ofsurface height distribution Sku, which are 3D surface roughnessparameters of the hard coat surface defined according to the invention,are obtained by analyzing the 3D surface profile (measured with SP-500)with a nanoscale 3D image processing software SPIP™ (manufactured byImage Metrology A/S).

The arithmetical mean slope angle Δa was determined by the methoddescribed below. The 3D surface profiles in two directions perpendicularto each other were each measured under the conditions described abovewith the surface profiler SP-500 (manufactured by Toray Engineering Co.,Ltd.). As regards each of the resulting surface profiles, the operations“display result”-“measure roughness”, the whole of the measured area,and the operation “measurement” were selected to calculate the values(Δa1,Δa2). The arithmetical mean slope angle Δa is the average of thevalues according to the formula Δa=(Δa1+Δa2)/2.

In a similar manner, the profile of the interface between the polyesterfilm and the hard coat layer is measured with the surface profilerSP-500 (manufactured by Toray Engineering Co., Ltd.) and a ×5 objectivelens in WSI mode. The profile of the interface is obtained by selectingthe “back surface” of an image obtained by the operations “refractiveindex” 1.52 and “data processing”-“gaussian filter”-“cut high frequency”30 μm.

The resulting curve of surface shape and the resulting curve ofinterface shape were vertically aligned, and the positions of theirregularities were checked.

When 10 projections of the interface coincided with 7 or moredepressions of the surface, the structure was determined as havingprojections of the polyester film surface immediately below depressionsof the hard coat surface. When 10 projections of the interface coincidedwith 7 or more projections of the surface, the structure was determinedas having projections of the polyester film surface immediately belowprojections of the hard coat surface.

The interface projection height was determined by the method describedbelow.

As regards the resulting curve of interface shape, the operations“display result”-“measure roughness”, the whole of the measured area,and the operation “measurement” were selected to obtain an Rz value asthe height.

(2) Abrasion Resistance

The hard coat layer surface was abraded with steel wool #0000 underdifferent loads. Under each constant load, the surface was abraded byreciprocating the steel wool 10 times (at a rate of 10 cm/second), andthe maximum load under which scratch resistance was observed (no scratchwas observed) was determined. A load of 2 kg/cm² was determined as apractically acceptable level.

(3) Haze

The haze was measured using a direct-reading haze computer manufacturedby Suga Test Instruments Co., Ltd. according to JIS K 7136.

(4) Heat Shrinkage Ratio (%) at 150° C. for 30 Minutes

The hard-coated film was cut into 10 mm-wide, 200 mm-long strips. A 100mm reference line was drawn at the longitudinal center of the strip, andthe strip was suspended in a 150° C. hot blast oven with 1 g of a loadapplied to its lower end in the longitudinal direction. In this state,the strip was allowed to stand for 30 minutes and then removed. Thelength (L1) of the original reference line on the sample and the length(L2) of the reference line after the treatment at 150° C. for 30 minuteswere measured with precision at an order of 0.1 mm. The value{(L1−L2)/L1}×100 was defined as the heat shrinkage ratio of the sample.The measurement was performed at 10 points along each of thelongitudinal direction of the hard-coated film-forming process and thedirection perpendicular thereto, and the measurements were averaged.

(5) Presence or Absence of Interference Iris Pattern

In order to eliminate the effect of back surface reflection, the backsurface opposite to the surface to be measured (the hard coat layer sidesurface) was roughed with sand paper No. 240 in the same manner as inthe measurement of surface reflectance and mean ripple amplitude. Thesample colored with a black magic marker was then placed 30 cmimmediately below a three-wave type fluorescent lamp (National Palook,three-wave broad daylight type (FL 15EX-N 15W)) in a dark room. Whilethe sample was visually observed from different observing points,evaluation was performed based on whether or not an iris pattern wasvisually observed.

There was no visible iris pattern: rank A

There was a very weak visible iris pattern: rank B;

There was a weak visible iris pattern: rank C; and

There was a strong clear visible iris pattern: rank D.

(6) Preparation of Antireflection Films

Antireflection films were prepared by the methods described below.

Antireflection Film A

Three parts of a coating composition containing tin-containing indiumoxide particles (ITO) (35.7% in solids content, multifunctional urethane(meth)acrylate/ITO particles (30 nm in average primary particlesize)=18/82) (EI-3 manufactured by Dai Nippon Toryo Co., Ltd.) wasdissolved in 10 parts of n-butyl alcohol and 7 parts of isopropylalcohol. The mixture was stirred to form a coating liquid. The coatingliquid was applied to the surface of the hard coat layer with a wirebar, dried at 80° C., and then irradiated with 1.0 J/cm² ultravioletlight so that the coating layer was hardened to form ahigh-refractive-index layer with a thickness of about 0.1 μm and arefractive index n of 1.68.

A coating liquid was then prepared by mixing 40 parts of a coatingcomposition containing a fluorine-containing copolymer(fluoroolefin-vinyl ether copolymer) (3% in solids content, JN-7215manufactured by JSR Corporation), 1 part of a colloidal silicadispersion (13 nm in average primary particle size, 30% in solidscontent, a methyl isobutyl ketone dispersion), and 0.1 parts of anothercolloidal silica dispersion (100 nm in average primary particle size,30% in solids content, a methyl isobutyl ketone dispersion). The coatingliquid was applied to the electrically-conductive layer 4 with a wirebar and dried and cured at 150° C. to form a low-refractive-index layerwith a thickness of about 0.1 μm and a refractive index n of 1.42, sothat an antireflection film was prepared.

Antireflection Film B

The low-refractive-index layer-forming coating composition prepared forthe antireflection film A was used and applied to the hard-coated filmso that it would form a 0.1 μl-thick layer after drying and hardening.

Antireflection Film C

Only the hard-coated film with neither high-refractive-index layer norlow-refractive-index layer was used as an antireflection film.

(7) Surface Reflectance

The antireflection films prepared as in (6) were measured by the methoddescribed below. A spectrophotometer model U-3410 (manufactured byHitachi, Ltd.) equipped with a 60 mmφ integrating sphere was used tomeasure the reflectance at an incidence angle of 10 degrees, and theminimum reflectance over the wavelength range of 400 to 750 nm wasdetermined as the surface reflectance.

In order to eliminate the effect of back surface reflection, the backsurface opposite to the surface to be measured (the hard coat layer sidesurface) was roughed with sand paper No. 240 and then colored with ablack magic marker so that the visible light average transmittance wouldbe reduced to 5% or less over the wavelength range of 400 to 600 nm.When the gloss of the back surface (at an incidence angle of 60° and anacceptance angle of 60°) was 10 or less after the treatment, the backsurface reflection was judged to have no influence. The gloss wasmeasured using a digital variable gloss meter UGV-5B (manufactured bySuga Test Instruments Co., Ltd.) according to JIS Z 8741.

(8) Coloration Irregularity Associated with Reflected Light

The prepared antireflection films were used and evaluated for thecoloration irregularity of reflected light by the same method as for (5)evaluation of the presence or absence of interference iris patterns,according to the criteria below.

There was no coloration irregularity: There was no coloration changeobserved in an evaluation area of 50 cm square: excellent;

There was slight coloration irregularity: There was coloration changeobserved in an evaluation area of at least 30 cm square and less than 50cm square: good;

There was weak coloration irregularity: There was coloration changeobserved in an evaluation area of at least 10 cm square and less than 30cm square: acceptable; and

There was strong coloration irregularity: There was coloration changeobserved in an evaluation area of less than 10 cm square: poor.

(9) Clear View Properties (Transmitted Image Sharpness)

The antireflection film was cut into A4 size pieces. The film piece wasfixed to the front face of the screen of a PDP television (TH-42PX500manufactured by Panasonic Corporation) placed in a dark room withcellophane tapes attached to the four corners of the film piece in suchmanner that the antireflection surface was placed on the viewer side.While an image was displayed on the screen of the television, thetransmitted image at the portion to which the antireflection film wasattached and the transmitted image at the portion with no antireflectionfilm were observed from a place 1.5 m apart from the front face of thetelevision and compared as to whether the transmitted image wasdegraded.

The transmitted image was clearly visible with no degradation:excellent;

The transmitted image was slightly blurred: good;

The transmitted image was blurred and less visible: acceptable; and

The transmitted image was not visible: poor.

(10) Transmittance at 380 nm

The transmittance of the antireflection film was determined at 380 nmwith a spectrophotometer U-3410 (manufactured by Hitachi, Ltd.) equippedwith a 460 integrating sphere 130-063 (manufactured by Hitachi Ltd.) anda 10-degree tilt spacer, and measurements at 10 points were averaged.

(11) Reflection-Reducing Effect 1

The antireflection film was cut into A4 size pieces. The film piece wasfixed to the front face of the screen of a PDP television (TH-42PX500manufactured by Panasonic Corporation) with cellophane tapes attached tothe four corners of the film piece in such manner that theantireflection surface was placed on the viewer side. Room lighting wasset at 400 to 500 lx, and the image of the viewer reflected on the frontface of the television was observed from a place 1.5 m apart from thetelevision in the off-state of the television.

The portion to which the antireflection film was attached was comparedwith the portion with no film based on the following criteria.

The outline of the eyes of the observer was not visible: excellent;

The outline of the eyes of the observer was barely visible, but theimage was not sharp as compared with the portion with no film: good; and

The outline of the eyes of the observer was visible: poor.

(12) Reflection-Reducing Effect 2

Reflection of a fluorescent lamp on the screen was evaluated in asimilar manner to that described in the article (11) under the lampremaining on in a room based on the criteria below.

The outline of the fluorescent lamp was completely blurred: excellent;

The outline of the fluorescent lamp was blurred: good; and

The fluorescent lamp was not blurred, and its outline was clearlyvisible: poor.

(13) Screen Glittering

The same setting as in (11) was used. The television was turned on, and“green” patterns were displayed on the screen. The degree of screenglittering was observed in the normal direction and visually evaluatedaccording to the criteria below.

There was no screen glittering: excellent;

The screen slightly glittered: good; and

The screen significantly glittered: poor.

EXAMPLES

The invention is more specifically described with the examples below,but not limited thereto.

Hard coat layer-forming coating compositions were prepared as describedbelow.

H-1

Main Component:

A mixture of dipentaerythritol hexaacrylate and dipentaerythritolpentaacrylate (KAYARAD-DPHA manufactured by Nippon Kayaku Co., Ltd.) 70%by weight;

Trimethylolpropane ethylene oxide-modified triacrylate (ARONIX(registered trademark) M-350 manufactured by Toagosei Co., Ltd.) 10% byweight; and

Completely alkylated melamine (Cymer 303 manufactured by Nippon CytecIndustries) 20% by weight

Based on 100 parts by weight of the main component,

Catalyst: Catalyst 602 (manufactured by Nippon Cytec Industries) 1 partby weight; and

Leveling agent: ARUFON-UP1000 (registered trademark) manufactured byToagosei Co., Ltd. 0.2 parts by weight

Viscosity of the coating composition: 2000 mPa·s at 25° C.; 150 mPa·s at100° C.

H-2

Main Component:

A mixture of dipentaerythritol hexaacrylate and dipentaerythritolpentaacrylate (KAYARAD-DPHA manufactured by Nippon Kayaku Co., Ltd.) 40%by weight;

Trimethylolpropane ethylene oxide-modified triacrylate (ARONIX M-350manufactured by Toagosei Co., Ltd.) 40% by weight; and

Completely alkylated melamine (Cymer 303 manufactured by Nippon CytecIndustries) 20% by weight

Additives:

Based on 100 parts by weight of the main component,

Catalyst: Catalyst 602 (manufactured by Nippon Cytec Industries) 1 partby weight; and

Leveling agent: ARUFON-UP1000 (manufactured by Toagosei Co., Ltd.) 0.2parts by weight

Viscosity of the coating composition: 800 mPa·s at 25° C.; 60 mPa·s at100° C.

H-3

Main Component:

A mixture of dipentaerythritol hexaacrylate and dipentaerythritolpentaacrylate (KAYARAD-DPHA manufactured by Nippon Kayaku Co., Ltd.) 20%by weight;

Trimethylolpropane ethylene oxide-modified triacrylate (ARONIX M-350manufactured by Toagosei Co., Ltd.) 60% by weight; and

Completely alkylated melamine (Cymer 303 manufactured by Nippon CytecIndustries) 20% by weight

Additives:

Based on 100 parts by weight of the main component,

Catalyst: Catalyst 602 (manufactured by Nippon Cytec Industries) 1 partby weight; and

Leveling agent: ARUFON-UP1000 (manufactured by Toagosei Co., Ltd.) 0.2parts by weight

Viscosity of the coating composition: 600 mPa·s at 25° C.; 40 mPa·s at100° C.

H-4

Main Component:

A mixture of dipentaerythritol hexaacrylate and dipentaerythritolpentaacrylate (KAYARAD-DPHA manufactured by Nippon Kayaku Co., Ltd.) 60%by weight;

Trimethylolpropane ethylene oxide-modified triacrylate (ARONIX M-350manufactured by Toagosei Co., Ltd.) 10% by weight;

Polyethylene glycol diacrylate (ARONIX M-240 manufactured by ToagoseiCo., Ltd.) 10% by weight; and

Completely alkylated melamine (Cymer 303 manufactured by Nippon CytecIndustries) 20% by weight

Additives:

Based on 100 parts by weight of the main component,

Catalyst: Catalyst 602 (manufactured by Nippon Cytec Industries) 1 partby weight; and

Leveling agent: ARUFON-UP1000 (manufactured by Toagosei Co., Ltd.) 0.2parts by weight

Viscosity of the coating composition: 1300 mPa·s at 25° C.; 100 mPa·s at100° C.

Example 1

Polyethylene terephthalate (hereinafter referred to as PET, with anintrinsic viscosity of 0.65 dl/g) chips were sufficiently dried undervacuum at 180° C. for 3 hours and then fed to a melt extruder. After thechips were melted at 285° C., the melt was extruded into a sheet througha T-shaped die. The sheet was cooled and solidified on a rotatingmirror-surface casting drum with a surface temperature of 20° C. bystatic electricity-applying casting method so that an unstretched sheetwas prepared. The resulting unstretched sheet was continuously stretchedin the longitudinal direction. In the longitudinal stretching process,the sheet was first preheated at 75° C. with a group of sequentiallyarranged rolls and then heated with a roll at 95° C. and stretched 3.5times, while the film surface was heated with a radiation heater. Thedrum surface side of the film had a refractive index of 1.645 and acrystallinity of 19% as measured by Raman method. The hard coatlayer-forming coating composition (H-1) was applied in a thickness of 20μm to the drum surface side of the film by metabar method. The film wasthen continuously introduced into a tenter, while both ends of the filmwere fixed. After the film was preheated at 70° C. for 15 seconds, thefilm was slightly stretched 1.2 times in the transverse direction at 75°C. and then stretched 3.3 times in the transverse direction at 95° C.The film was continuously heat-treated in a heat treatment zone at 220°C. for 25 seconds, while the coating layer was hardened and while thefilm was relaxed by 5%.

The resulting hard-coated film had a hard coat layer with a thickness of5 μm.

In the hard-coated film, the hard coat surface and the PET film surfacein contact with the hard coat layer each had irregularities, andprojections of the hard coat layer surface coincided with depressions ofthe PET film surface. Sa and Sku of the hard coat surface was 41 nm and2.2, respectively.

The hard-coated film in the scope of the invention had a high level ofabrasion resistance and was completely free from interference irispatterns. The hard coat surface of the hard-coated film was subjected tothe process according to (6) Preparation of Antireflection Films in theSection of “Characterization Methods and Effect Evaluation Methods,” sothat an antireflection film A was prepared.

As shown in Table 2, the antireflection film had neither colorationirregularity nor screen glittering and had a high level of clear viewproperties and the effect of suppressing reflection.

Examples 2 and 3

Hard-coated films were prepared using the process of Example 1, exceptthat the hard coat layer-forming coating composition H-2 (Example 2) orH-4 (Example 3) was used instead. In the hard-coated films, Sa and Skuof the hard coat surface was 18 nm and 1.6 (Example 2), respectively,and 56 nm and 1.9 (Example 3), respectively. Example 2 was slightlyinferior in surface hardness and interference iris pattern butsufficiently free from practical problems. These films were used to formantireflection films in the same manner as in Example 1. As shown inTable 2, the antireflection films had properties sufficiently practicalin terms of coloration irregularity, clear view properties, andsuppressing of screen glittering and reflection.

The hard-coated film of Example 3 was used to form antireflection filmsB and C. As shown in Table 2, the antireflection films were slightlyreduced in the reflection-suppressing effect but practically free fromproblems.

Examples 4 to 6 and Comparative Example 1

Hard-coated films were prepared using the process of Example 3, exceptthat after the hard coat layer was hardened under the relaxation by 5%in the heat treatment zone, the film was further continuously relaxed at230° C. for 15 seconds by 3% (Example 4), 5% (Example 5), 7% (Example6), or 10% (Comparative Example 1). As shown in Table 1, the hard coatedfilms differed in Sa of the hard coat layer surface depending on thedegree of the relaxation, and the relaxation by 10% produced Sa of 163nm. The hard-coated films each had a structure in which projections ofthe hard coat surface coincided with projections of the PET filmsurface. The hard-coated film obtained in each of Examples 4 to 6 andComparative Example 1 had sufficient abrasion resistance and is freefrom interference iris patterns. Each of these hard-coated films wasused to form an antireflection film according to Examples 1 and 3. Theeffect of suppressing reflection was particularly high in Examples 4 to6 where Sa and Sku of the hard coat layer surface fell within the rangeaccording to the invention. When Sa of the hard coat layer surfaceexceeded the range (Comparative Example 1), an increase in haze wasobserved, the transmitted image became slightly unclear, and screenglittering was significant.

Comparative Example 2

A hard-coated film was prepared using the process of Example 1, exceptthat the hard coat layer-forming coating composition H-3 was usedinstead. The hard-coated film had irregularities. However, Sa and Skuwere relatively small due to the coating composition, and it hadinsufficient surface hardness and a visible interference iris pattern.The hard coated film was used to form an antireflection film A in thesame manner as in Example 1. The antireflection film had highly visiblecoloration irregularity, and its reflection-suppressing effect wasinsufficient.

Comparative Example 3

A hard-coated film was prepared using the process of Example 1, exceptthat the slight stretching temperature was 95° C. As shown in Table 1,the hard-coated film had no irregularities on the hard coat layersurface or on the PET film surface, and Sa and Sku were less than therange. It also had a clearly-visible interference iris pattern. Thehard-coated film was used to form an antireflection film A in the samemanner as in Example 1. As shown in Table 2, the resultingantireflection film had significant coloration irregularity and showedsignificant reflection.

Comparative Example 4

A hard-coated film was prepared using the process of Example 1, exceptthat the relaxation was not performed in the heat treatment zone duringthe hardening of the hard coat layer. Since the relaxation was notperformed in response to the hardening and shrinkage of the hard coatlayer, the film had cracks in the hard coat layer and was practicallyunusable.

Comparative Example 5

An adhesive polyester film (Lumirror (registered trademark) U46manufactured by Toray Industries, Inc.) was used. The hard coatlayer-forming coating composition shown below was applied to the film,then dried at 80° C. for 1 minute, and irradiated with 350 mJ/cm² ofultraviolet rays, so that a hard-coated film with a 5 μm-thick hard coatlayer was prepared.

Hard Coat Layer-Forming Coating Composition:

A mixture of dipentaerythritol hexaacrylate and dipentaerythritolpentaacrylate (KAYARAD-DPHA manufactured by Nippon Kayaku Co., Ltd.) 30%by weight;

Trimethylolpropane ethylene oxide-modified triacrylate (ARONIX M-350manufactured by Toagosei Co., Ltd.) 15% by weight;

Polyester acrylate (ARONIX M7100 manufactured by Toagosei Co., Ltd.) 4%by weight;

Photopolymerization initiator (Irgacure 184 manufactured by CibaSpecialty Chemicals Inc.) 1% by weight;

Toluene 25% by weight; and

Methyl ethyl ketone 25% by weight.

In the hard-coated film, both the hard coat layer surface and the PETfilm surface were flat, and Sa and Sku of the hard coat layer surfacewere each less than the range according to the invention. Aninterference iris pattern was clearly observed in the hard-coated film.The hard-coated film was used to form an antireflection film A in thesame manner as in Example 1. The antireflection film was inferiorbecause of significant coloration irregularity and reflection.

Comparative Examples 6 and 7

Hard-coated films were prepared using the process of Comparative Example5, except that based on 100 parts by weight of the hard coatlayer-forming compositions (exclusive of the solvents), 1 part by weight(Comparative Example 6) or 5 parts by weight (Comparative Example 7) ofstyrene-acrylic crosslinked organic particles with an average particlesize of 5 μm and a particle refractive index of 1.52 were added to thehard coat-forming coating composition. The hard-coated films each hadprojections formed by the particles in the hard coat layer and had Sa of351 nm (Comparative Example 6) and Sa of 260 nm (Comparative Example 7),and an Sku of 2.9 (Comparative Example 6) and an Sku of 6.5 (ComparativeExample 7), respectively. The hard-coated films were each used to forman antireflection film A, B, or C in the same manner as in Example 3.The characteristics of the resulting antireflection films are shown inTable 2. The antireflection film produced with the hard-coated film ofComparative Example 6 or 7 showed significant screen glittering,regardless of the structure. The antireflection film using hard-coatedfilm of Comparative Example 7 containing a relatively large amount ofparticles had a high haze and made the transmitted image blurred.

Examples 7 and 8 and Comparative Example 8 and 9

Hard-coated films were prepared using the process of Example 1, exceptthat the draw ratio and the stretching temperature in the longitudinalstretching process were changed so that a longitudinally-stretched filmwith a refractive index of 1.615 and a crystallinity of 12% (ComparativeExample 8), a refractive index of 1.625 and a crystallinity of 18%(Comparative Example 9), a refractive index of 1.63 and a crystallinityof 17% (Example 7), or a refractive index of 1.655 and a crystallinityof 22% (Example 8) was used. In Comparative Example 8, the interface hadno irregularities. In Comparative 9, the interface has irregularities,but Sa and Sku of the hard coat surface was not sufficient. Aninterference iris pattern was observed in both cases. In contrast, thehard-coated films prepared under the conditions of Examples 7 and 8,respectively, each had satisfactory irregularities and Sa and Sku eachfalling within the range according to the invention. The hard-coatedfilms were each used to form an antireflection film A in the same manneras in Example 1. As shown in Table 2, the antireflection films ofComparative Examples 8 and 9 each had Sa and Sku each falling outsidethe range according to the invention and were insufficient in terms ofthe effect of suppressing coloration irregularity and reflection. Theantireflection films produced with the hard-coated films of Examples 7and 8 with Sa and Sku each falling within the range according to theinvention each had practically satisfactory Characteristics.

Example 9

A hard-coated film was prepared using the process of Example 1, exceptthat the PET chips were replaced with PET (with an intrinsic viscosityof 0.63 dl/g) chips containing 0.8 wt % of Cyasorb (registeredtrademark) 3638 (manufactured by Cytec Industries Inc.) as anultraviolet ray-absorbing agent. As shown in Table 1, the hard-coatedfilm had satisfactory Sa and Sku of the hard coat surface and also had atransmittance of 2.6% at a wavelength of 380 nm. The hard-coated filmwas used to form an antireflection film A in the same manner as inExample 1. As shown in Table 2, all the characteristics of theantireflection film reached a practical level, and the antireflectionfilm had the effect of blocking ultraviolet rays.

TABLE 1 Relationship between Presence Presence or Presence orsurface/interface Heat or absence absence of absence of irregularitiesInter- shrinkage Abra- of interface surface Projections/ Surface faceratio at sion inter- irregularities irregularities depressions: A Sa Sa150° C. for resis- ference Presence: ◯ Presence: ◯ Projections/ (Sa1)(Sa2) Sa2 Surface Surface Haze 30 minutes tance iris Absence: — Absence:— projections: B (nm) (nm) Sa1 Sku Δa (%) (%) (kg/cm²) pattern Example 1◯ ◯ A 41 305 7.4 2.2 0.38 1.4 1.9 2.7 A Example 2 ◯ ◯ A 18 274 15.2 1.60.24 0.8 1.8 2.1 B Example 3 ◯ ◯ A 56 316 5.6 1.9 0.42 1.7 1.8 2.6 AExample 4 ◯ ◯ B 74 324 4.4 2.5 0.46 1.8 0.7 2.7 A Example 5 ◯ ◯ B 96 3313.4 2.8 0.57 2.1 0.2 2.7 A Example 6 ◯ ◯ B 121 343 2.8 3.1 0.68 2.9 0.12.6 A Comparative ◯ ◯ B 163 358 2.2 3.7 0.77 4.4 0.0 2.5 A Example 1Comparative ◯ ◯ A 14 186 13.2 1.3 0.11 0.7 1.9 1.3 C Example 2Comparative — — — 8 152 19.0 1.1 0.08 0.6 1.8 2.7 D Example 3Comparative Hard coat layer cracking Example 4 Comparative — — — 7 7 11.1 0.05 0.8 0.8 2.6 D Example 5 Comparative — ◯ — 351 10 0.03 2.9 1.292.6 0.8 2.7 A Example 6 Comparative — ◯ — 260 10 0.04 6.5 1.83 8.5 0.82.7 A Example 7 Comparative — — — 8 13 1.6 1.1 0.08 0.6 1.8 2.8 DExample 8 Comparative ◯ ◯ A 13 148 11.4 1.2 0.11 0.7 1.7 2.8 C Example 9Example 7 ◯ ◯ A 29 286 9.9 1.7 0.28 1.2 1.7 2.7 B Example 8 ◯ ◯ A 63 3215.1 2.6 0.40 1.5 1.7 2.7 A Example 9 ◯ ◯ A 44 311 7.1 2.1 0.37 1.6 1.82.7 A

TABLE 2 Clear view Transmittance Surface properties (%) atReflection-reducing Antireflection reflectance Haze Coloration(transmitted image wavelength of effect Screen film (%) (%) irregularitysharpness) 380 nm 1 2 glittering Example 1 A 1.2 1.8 Excellent Excellent— Good Good Excellent Example 2 A 1.0 1.4 Good Excellent — Good GoodExcellent Example 3 A 1.3 2.2 Excellent Good — Excellent Good ExcellentB 1.5 2.0 Excellent Excellent — Excellent Good Excellent C 3.9 1.7Excellent Excellent — Good Excellent Excellent Example 4 A 1.3 2.3Excellent Good — Excellent Excellent Excellent Example 5 A 1.4 2.4Excellent Good — Excellent Excellent Excellent B 2.4 2.3 Excellent Good— Excellent Excellent Excellent C 3.9 2.1 Excellent Good — ExcellentExcellent Excellent Example 6 A 1.5 3.2 Excellent Good — ExcellentExcellent Good Comparative A 1.5 4.6 Excellent Acceptable — ExcellentExcellent Acceptable Example 1 B 2.7 4.5 Excellent Acceptable —Excellent Excellent Acceptable C 4.0 4.4 Excellent Acceptable —Excellent Excellent Acceptable Comparative A 0.9 1.2 AcceptableExcellent — Acceptable Acceptable Excellent Example 2 Comparative A 0.91.0 Poor Excellent — Poor Poor Excellent Example 3 Comparative — — — — —— — — — Example 4 Comparative A 0.8 1.1 Poor Excellent — Poor PoorExcellent Example 5 Comparative A 1.6 3.0 Excellent Good — ExcellentExcellent Poor Example 6 B 2.7 2.7 Excellent Good — Excellent ExcellentPoor C 5.1 2.6 Excellent Good — Excellent Excellent Poor Comparative A1.8 9.1 Excellent Poor — Excellent Excellent Poor Example 7 B 2.8 8.8Excellent Poor — Excellent Excellent Poor C 4.9 8.5 Excellent Poor —Excellent Excellent Poor Comparative A 0.8 1.1 Poor Excellent — PoorPoor Excellent Example 8 Comparative A 0.9 1.3 Acceptable Excellent —Acceptable Acceptable Excellent Example 9 Example 7 A 1.1 1.6 GoodExcellent — Good Good Excellent Example 8 A 1.4 1.9 Excellent Excellent— Excellent Good Excellent Example 9 A 1.3 2.0 Excellent Excellent 2.6Good Good Excellent Antireflection films A to C: The antireflectionfilms were prepared using each of the films prepared in Examples 1 to 9and Comparative Examples 1 to 9 according to (6) Preparation ofAntireflection Films in the section of “Characterization Methods andEffect Evaluation Methods.”

INDUSTRIAL APPLICABILITY

The hard-coated film of the invention has good adhesion to the hard coatlayer and high light resistance and is substantially free frominterference iris patterns. When used for an antireflection film, thehard-coated film can effectively reduce screen glittering and externallight reflection without loss of image sharpness. Therefore, thehard-coated film is useful as an antireflection film substrate forliquid crystal displays, plasma displays, or the like, or as a base filmfor touch panels, window films, solar battery members, nameplates, orthe like.

1. A hard-coated film, comprising: a polyester film; and a hard coat layer placed on at least one side of the polyester film, wherein the hard coat layer comprises a multi-functional acrylate, another monofunctional or bifunctional acrylate, and a melamine-based crosslinking agent, the hard-coated film has a heat shrinkage ratio of at most 0.8% at 150° C. for 30 minutes in at least one direction, the hard coat layer has a surface with irregularities, an interface between the polyester film and the hard coat layer has irregularities on the polyester film side, such that projections of the irregularities on the polyester film side coincide with projections of the hard coat surface profile in the thickness direction, and the surface of the hard coat layer has 3D surface roughness parameters comprising an arithmetical mean deviation of surface Sa of from 15 nm to less than 150 nm and a kurtosis of surface height distribution Sku of from 1.5 to
 5. 2. The hard-coated film of claim 1, wherein the interface between the polyester film and the hard coat layer has irregularities on the polyester film side, and projections of the irregularities on the polyester film side coincide with depressions of the hard coat surface profile in a thickness direction.
 3. The hard-coated film of claim 1, wherein the hard coat layer is a thermally hardened layer.
 4. The hard-coated film of claim 1, wherein the polyester film contains ultraviolet ray-absorbing agents.
 5. The hard-coated film of claim 1, wherein the irregularities of the hard coat layer are formed without the aid of particles in the hard coat layer and the polyester film.
 6. The hard-coated film of claim 1, wherein the hard coat layer surface has an average Δa of from 0.2 degrees to 1.0 degree, wherein the average Δa is calculated from the formula Δa=(Δa1+Δa2)/2, wherein Δa1 and Δa2 are arithmetical mean slope angles of the hard coat layer surface in two directions perpendicular to each other, respectively.
 7. The hard-coated film of claim 1, wherein the hard coat layer surface has an Sa2/Sa1 ratio of from 2 to 20, wherein Sa1 is the arithmetical mean deviation of surface (Sa) of the hard coat layer surface, and Sa2 is the arithmetical mean deviation of surface (Sa) of the interface between the polyester film and the hard coat layer, concerning the 3D surface roughness parameters.
 8. The hard-coated film of claim 1, wherein Sku of the hard coat layer is from 1.5 to
 3. 9. The hard-coated film of claim 1, wherein the hard-coated film has a haze of less than 3%.
 10. An antireflection film, comprising: the hard-coated film of claim 1; and a low-refractive-index layer with a refractive index of at most 1.45 that is formed on the hard coat layer of the hard-coated film, optionally with a high-refractive-index layer with a refractive index of at least 1.55 interposed between the hard coat layer and the low-refractive-index layer.
 11. The antireflection film of claim 10, wherein it has a haze of less than 4% and a transmittance of at most 5% at a wavelength of 380 nm. 